HOST DEFENSE AND THE HEPATIC PENTOSE CYCLE

不同肝细胞（枯否细胞、内皮细胞和 实质）对于代谢支持和非特异性 宿主对创伤和感染的免疫反应。 内毒素 激活肝非实质细胞（枯否细胞和内皮细胞）， 与这些细胞对葡萄糖的利用率升高有关。 的 葡萄糖代谢增强的确切作用和功能重要性 在不同的肝细胞感染过程中，知之甚少。 本项目的长期目标是阐明 通过戊糖循环调节葡萄糖代谢， 肝细胞在细菌感染。 拟议的研究重点 细菌内毒素对戊糖循环的影响， 用于支持增强的清道夫功能的调节位点， 细菌杀灭和抗氧化损伤的保护机制 枯否细胞、肝内皮细胞和肝实质细胞。 三个假设 将测试：（1）增加巨噬细胞的葡萄糖利用率 在感染期间有助于戊糖循环活性的增强， 它是一个主要的调节位点， 单核吞噬细胞的完全激活的功能状态。 (2)的 肝内皮细胞感染时戊糖循环的上调 细胞是一个重要的保护机制，对氧化组织 肝损伤。 (3)内毒素的作用是由 上调戊糖循环的糖调节激素和细胞因子 以细胞特异性的方式。 为了解决前两个假设， 在体内实验性内毒素血症，葡萄糖摄取， 磷酸化和进入戊糖循环将在体内测定 在离体枯否细胞、肝内皮细胞和肝实质细胞中， 细胞，使用同位素示踪技术。 内毒素作用的靶点 通量产生酶（主要是葡萄糖-6-磷酸脱氢酶和 己糖激酶）将通过测量最大活性来确定， 动力学参数，酶合成速率，翻译后 修饰mRNA的表达。 戊糖循环的活动将 与超氧化物的产生、氧自由基的消除有关 以及各种肝细胞中的大分子合成。 为了测试第三个 假设，不同的激素和细胞因子将在体内施用 大鼠，或体外Kupffer，肝内皮和 实质细胞，并评估戊糖循环的活性。 我们的主要目标是阐明的生化特性， 戊糖循环的启动状态及其由内分泌和 不同肝细胞的旁分泌系统。 本研究将提供 有价值的信息，为新的治疗方法，以支持 严重感染和创伤中宿主防御相关肝功能， 最终将有助于我们逆转多器官 失败综合症

Coordinated function of different hepatic cells (Kupffer, endothelial and parenchymal) is essential for the metabolic support and nonspecific immune response of the host to trauma and infections. Endotoxemia activates hepatic nonparenchymal cells (Kupffer and endothelial) and is associated with an elevated glucose utilization by these cells. The exact role and functional importance of augmented glucose metabolism during infection in the different hepatic cells are poorly understood. The long term objective of this project is to elucidate the role and regulation of glucose metabolism through the pentose cycle in various hepatic cells during bacterial infections. The proposed study focuses on the effect of bacterial endotoxin on the pentose cycle as a primary regulatory site for the support of augmented scavenger function, bacterial killing and protective mechanisms against oxidative damage in Kupffer, hepatic endothelial and parenchymal cells. Three hypotheses will be tested: (1) The elevated glucose utilization of macrophages during infection subserves the enhanced activity of the pentose cycle, which is a primary regulatory site for the development of primed and fully activated functional state of the mononuclear phagocytes. (2) The upregulation of pentose cycle during infection in hepatic endothelial cells is an important protective mechanism against oxidative tissue injury of the liver. (3) The effect of endotoxin is mediated by glucoregulatory hormones and cytokines which upregulate the pentose cycle in a cell specific manner. To address the first two hypotheses, following in vivo experimental endotoxemia, glucose uptake, phosphorylation and entry in the pentose cycle will be determined in vivo and in vitro in isolated Kupffer, hepatic endothelial, and parenchymal cells, using isotope tracer techniques. The targets of endotoxin on the flux generating enzymes (primarily glucose-6-phosphate dehydrogenase and hexokinase) will be determined by measuring the maximal activities and kinetic parameters, enzyme synthesis rates, posttranslational modifications expression of mRNA. The activity of the pentose cycle will be correlated with superoxide production, elimination of oxygen radicals and macromolecule synthesis in various hepatic cells. To test the third hypothesis, different hormones and cytokines will be administered in vivo to rats, or in vitro to cultures of Kupffer, hepatic endothelial and parenchymal cells, and the activity of pentose cycle will be assessed. Our primary goal is to elucidate the biochemical characteristics of the primed state of the pentose cycle and its regulation by the endocrine and paracrine system in different hepatic cells. This study will provide valuable information for new therapeutic approaches for the support of host defense related hepatic function in severe infection and trauma, and will eventually contribute to our ability to reverse the multiorgan failure syndrome.